As a vehicle drive unit, a device has been devised in which the left and right axles of a vehicle are connected to a differential apparatus and drive power is transmitted to the differential apparatus via a speed reduction mechanism using an electric motor coaxially disposed on the outer circumferential side of one of the axles (for example, refer to Patent document 1).
This drive unit 100 is, as shown in FIG. 35, equipped with an electric motor 102 for driving axles, a planetary gear reducer 112 for reducing the drive rotation speed of this electric motor 102, and a differential apparatus 113 for distributing the output of this planetary gear reducer 112 to the left and right axles 110A and 110B of a vehicle, wherein the planetary gear reducer 112 and the electric motor 102 are disposed coaxially with each other on the outer circumferential side of the axle 110B, one of the axles connected to the differential apparatus 113. Furthermore, the sun gear 121 and the planetary carrier 123 of the electric motor 112 are connected to the rotor 115 of the electric motor 102 and the differential case 131 of the differential apparatus 113, respectively, the ring gear 124 of the planetary gear reducer 112 is rotatably accommodated in the reducer case 111 that is secured to a vehicle body, and a hydraulic brake 128 for applying a braking force to the ring gear 124 by engaging the ring gear 124 with the reducer case 111 is provided between the ring gear 124 and the reducer case 111.
When the braking force is applied to the ring gear 124 by the hydraulic brake 128, the ring gear 124 is secured to the reducer case 111, and the drive power input from the rotor 115 of the electric motor 102 to the sun gear 121 is transmitted to the differential case 131 of the differential apparatus 113 while speed is reduced by a preset reduction ratio. The drive power transmitted to the differential case 131 is distributed to the left and right axles 110A and 110B of the vehicle by the differential apparatus 113. Moreover, when the braking force applied from the hydraulic brake 128 is shut off, the ring gear 124 rotates freely with respect to the reducer case 111. Hence, for example, when the braking force applied by the hydraulic brake 128 is shut off in a state in which the rotation speed of the axles 110A and 110B is higher than that required for the driving of the electric motor 102, the ring gear 124 idly rotates inside the reducer case 111 depending on extra rotation on the sides of the axles 110A and 110B, and the rotations of the axles 110A and 110B are not input to the electric motor 102. Hence, in the case that the driving and regeneration of the electric motor 102 are not necessary, accompanied rotation of the electric motor 102 can be prevented by shutting off the application of the braking force of the hydraulic brake 128, whereby improvement in fuel consumption is attained.
FIG. 37 is an overall view showing a hybrid vehicle described in Patent document 2. Furthermore, FIG. 38 is a view showing a torque transmission mechanism for use in the hybrid vehicle described in Patent document 2. The hybrid vehicle H shown in FIGS. 37 and 38 can travel by virtue of at least either one of an engine 101 and a motor 102. The hybrid vehicle H is equipped with a clutch mechanism 106, a connection control mechanism 141 and a rotation speed control mechanism 122.
In the clutch mechanism 106, a one-way clutch 105 for transmitting the torque of the motor 102 to the drive side in the case that the vehicle starts traveling from its stop state and a hydraulic clutch 104 for hydraulically connecting the output shaft 121 of the motor 102 to a drive shaft 103 are provided in parallel with the drive shaft 103. The connection control mechanism 141 disengages the hydraulic clutch 104 in the case that the rotation speed of the motor 102 is equal to or more than its allowable rotation speed and reengages the hydraulic clutch 104 in the case that an operation condition in which the rotation of the motor 102 is allowable is obtained. As shown in FIG. 39, at the time of the reengagement, the rotation speed control mechanism 122 performs control in which the rotation speed of the motor 102 is raised sharply to a rotation speed (changeover rotation speed r) lower than a target rotation speed R by a predetermined value and then the rotation speed of the motor 102 is raised gradually to the target rotation speed R.
In this hybrid vehicle H, by virtue of the control performed by the rotation speed control mechanism 122, a phenomenon in which the rotation speed of the motor 102 overshoots the target rotation speed R can be avoided, and the output shaft 121 of the motor 102 is smoothly engaged with the one-way clutch 105. Hence, a mechanical shock that occurs in the case that the output shaft 121 of the motor 102 is suddenly engaged with the one-way clutch 105 can be avoided.